//! Macros that can be used to improve your life with regards to crypto.

use derive_deftly::define_derive_deftly;

// NOTE: We will require a define_rsa_keypair for the future so the relay legacy RSA keys can be

// declared.

/// Create an ed25519 keypair wrapper given a visibility and a struct name.

///

/// # Syntax:

/// ```rust,ignore

/// define_ed25519_keypair(<visibility> <prefix>)

/// ```

///

/// This macro creates a struct tuple named `<prefix>Keypair` which contains the lower-level

/// cryptographic keypair for an ed25519 keypair. It derives the deftly Ed25519Keypair template

/// which in turn creates `<prefix>PublicKey` along a series of useful methods.

///

/// The keypair is NOT clonable by design in order to avoid duplicating secret key material.

///

/// # Example:

///

/// ```rust

/// use tor_key_forge::define_ed25519_keypair;

///

/// define_ed25519_keypair!(NonPublicSigning);

/// define_ed25519_keypair!(pub PublicSigning);

/// define_ed25519_keypair!(pub(crate) CratePublicSigning);

/// ```

///

/// The above results in `NonPublicSigningKeypair` and `NonPublicSigningPublicKey` struct being

/// created and usable with a series of useful methods. Same for the other defines.

///

/// You can then use these objects like so:

///

/// ```rust

/// # use tor_llcrypto::rng::FakeEntropicRng;

/// # let mut rng = FakeEntropicRng(rand::rng());

/// use rand::Rng;

/// use tor_key_forge::Keygen;

/// use tor_key_forge::define_ed25519_keypair;

/// use tor_llcrypto::pk::ValidatableSignature;

/// use tor_llcrypto::pk::ed25519::Ed25519SigningKey;

///

/// define_ed25519_keypair!(

///     /// Our signing key.

///     MySigning

/// );

///

/// let signing_kp = MySigningKeypair::generate(&mut rng).expect("Invalid keygen");

/// let signing_pubkey = signing_kp.public();

/// // Lets sign this wonderful message.

/// let message = "Workers want rights, not your opinion".as_bytes();

/// let sig = signing_kp.sign(&message);

///

/// // You can then verify either directly with the keypair or the public key.

/// assert!(signing_kp.verify(sig, &message));

/// assert!(signing_pubkey.verify(sig, &message));

/// ```

#[macro_export]

macro_rules! define_ed25519_keypair {

    ($(#[ $docs_and_attrs:meta ])*

     $vis:vis $base_name:ident) => {

        $crate::macro_deps::paste! {

            #[derive($crate::derive_deftly::Deftly)]

            #[derive_deftly($crate::macro_deps::Ed25519Keypair)]

            #[deftly(kp(pubkey = $base_name "PublicKey"))]

            #[non_exhaustive]

            $(#[ $docs_and_attrs ])*

            $vis struct [<$base_name "Keypair">]($crate::macro_deps::ed25519::Keypair);

        }

    };

}

define_derive_deftly! {

    /// Implement set of helper functions around a type wrapping an ed25519::Keypair.

    export Ed25519Keypair for struct:

    // Enforce that the object has a single field. We want to avoid the implementer to start

    // storing metadata or other things in this object that is meant specifically to be

    // a semantic wrapper around an Ed25519 keypair.

    ${if not(approx_equal(${for fields { 1 }}, 1)) { ${error "Single field only"}}}

    ${define KP_NAME $( $fname )}

    ${define PK_NAME ${tmeta(kp(pubkey)) as ident}}

    /// Public key component of this keypair. Useful if we move the public key around,

    /// it then keeps it semantic with the name and less prone to errors.

    #[derive(Clone, Debug, PartialEq, Eq)]

    #[derive($crate::macro_deps::derive_more::From, $crate::macro_deps::derive_more::Into)]

    #[non_exhaustive]

    $tvis struct $PK_NAME ($tvis $crate::macro_deps::ed25519::PublicKey);

    impl $PK_NAME {

        /// Verify the signature of a given message.

        #[allow(unused)]

            use $crate::macro_deps::ValidatableSignature;

            $crate::macro_deps::ed25519::ValidatableEd25519Signature::new(self.0, sig, text).is_valid()

        }

    }

    impl $crate::macro_deps::ed25519::Ed25519PublicKey for $PK_NAME {

            self.0

        }

    }

    // We don't expect all implementations to use all code.

    #[allow(unused)]

    impl $ttype {

        /// Build the raw inner public key into the wrapper public key object.

            $PK_NAME((&self.$KP_NAME).into())

        }

        /// Verify the signature of a given message.

            use $crate::macro_deps::ValidatableSignature;

            $crate::macro_deps::ed25519::ValidatableEd25519Signature::new(

                self.0.verifying_key(), sig, text

            ).is_valid()

        }

        /// Return a Ed25519Identity built from this keypair.

            $crate::macro_deps::ed25519::Ed25519Identity::from(&self.public().0)

        }

    }

    impl From<$crate::macro_deps::ed25519::Keypair> for $ttype {

            Self(kp)

        }

    }

    impl $crate::macro_deps::ed25519::Ed25519PublicKey for $ttype {

            self.0.public_key()

        }

    }

    impl $crate::macro_deps::ed25519::Ed25519SigningKey for $ttype {

            self.0.sign(msg)

        }

    }

    /// Implementing EncodableItem, ToEncodableKey and Keygen allows this wrapper key to be stored

    /// in a keystore.

    impl $crate::ItemType for $ttype {

            $crate::KeyType::Ed25519Keypair.into()

        }

    }

    impl $crate::EncodableItem for $ttype {

            self.$KP_NAME.as_keystore_item()

        }

    }

    impl $crate::ToEncodableKey for $ttype {

        type Key = $crate::macro_deps::ed25519::Keypair;

        type KeyPair = $ttype;

            self.$KP_NAME

        }

            Self(key)

        }

    }

    impl $crate::Keygen for $ttype {

            Ok(Self { $KP_NAME: $crate::macro_deps::ed25519::Keypair::generate(&mut rng) })

        }

    }

}

/// Create a curve25519 keypair wrapper given a visibility and a struct name.

///

/// # Syntax:

/// ```rust,ignore

/// define_curve25519_keypair(<visibility> <prefix>)

/// ```

///

/// This macro creates a struct tuple named `<prefix>Keypair` which contains the lower-level

/// cryptographic keypair for a curve25519 keypair. It derives the deftly Curve25519Keypair template

/// which in turn creates `<prefix>PublicKey` along a series of useful methods.

///

/// The keypair is NOT clonable by design in order to avoid duplicating secret key material.

///

/// # Example:

///

/// ```rust

/// use tor_key_forge::define_curve25519_keypair;

///

/// define_curve25519_keypair!(NonPublicEnc);

/// define_curve25519_keypair!(pub PublicEnc);

/// define_curve25519_keypair!(pub(crate) CratePublicEnc);

/// ```

///

/// The above results in `NonPublicEncKeypair` and `NonPublicEncPublicKey` struct being created and

/// usable with a series of useful methods.

///

/// You can then use these objects like so:

///

/// ```rust

/// # use tor_llcrypto::rng::FakeEntropicRng;

/// # let mut rng = FakeEntropicRng(rand::rng());

/// # use rand::Rng;

/// use tor_key_forge::define_curve25519_keypair;

/// use tor_key_forge::Keygen;

///

/// define_curve25519_keypair!(

///     // This is Alice's keypair.

///     AliceEnc

/// );

/// define_curve25519_keypair!(BobEnc);

///

/// let alice_kp = AliceEncKeypair::generate(&mut rng).expect("Failed alice keygen");

/// let bob_kp = BobEncKeypair::generate(&mut rng).expect("Failed bob keygen");

///

/// // Using the public key wrapper

/// let alice_shared_secret = alice_kp.diffie_hellman(bob_kp.public());

/// // Using the direct curve25519::PublicKey.

/// let bob_shared_secret = bob_kp.diffie_hellman(&alice_kp.public().0);

///

/// assert_eq!(alice_shared_secret.as_bytes(), bob_shared_secret.as_bytes());

/// ```

#[macro_export]

macro_rules! define_curve25519_keypair {

    ($(#[ $docs_and_attrs:meta ])*

    $vis:vis $base_name:ident) => {

        $crate::macro_deps::paste! {

            #[derive($crate::derive_deftly::Deftly)]

            #[derive_deftly($crate::macro_deps::Curve25519Keypair)]

            #[deftly(kp(pubkey = $base_name "PublicKey"))]

            #[non_exhaustive]

            $(#[ $docs_and_attrs ])*

            $vis struct [<$base_name "Keypair">]($crate::macro_deps::curve25519::StaticKeypair);

        }

    };

}

define_derive_deftly! {

    /// Implement set of helper functions around a type wrapping an ed25519::Keypair.

    export Curve25519Keypair for struct:

    // Enforce that the object has a single field. We want to avoid the implementer to start

    // storing metadata or other things in this object that is meant specifically to be

    // a semantic wrapper around an Curve25519 keypair.

    ${if not(approx_equal(${for fields { 1 }}, 1)) { ${error "Single field only"}}}

    ${define KP_NAME $( $fname )}

    ${define PK_NAME ${tmeta(kp(pubkey)) as ident}}

    /// Public key component of this keypair. Useful if we move the public key around,

    /// it then keeps it semantic with the name and less prone to errors.

    #[derive(Clone, Debug, PartialEq, Eq)]

    #[derive($crate::macro_deps::derive_more::From, $crate::macro_deps::derive_more::Into)]

    #[non_exhaustive]

    $tvis struct $PK_NAME ($crate::macro_deps::curve25519::PublicKey);

    impl std::borrow::Borrow<$crate::macro_deps::curve25519::PublicKey> for $PK_NAME {

        #[inline]

        fn borrow(&self) -> &$crate::macro_deps::curve25519::PublicKey {

            &self.0

        }

    }

    impl $ttype {

        /// Build the raw inner public key into the wrapper public key object.

        $tvis fn public(&self) -> $PK_NAME {

            $PK_NAME(self.$KP_NAME.public.clone())

        }

        /// Wrapper around the diffie_hellman() function of the underlying type. This is pretty fun

        /// because it accepts both the PK_NAME wrapper or the raw inner curve25519::PublicKey.

        $tvis fn diffie_hellman<T>(&self, pk: T) -> $crate::macro_deps::curve25519::SharedSecret

        where

            T: std::borrow::Borrow<$crate::macro_deps::curve25519::PublicKey>

        {

            self.$KP_NAME.secret.diffie_hellman(pk.borrow())

        }

    }

    impl From<$crate::macro_deps::curve25519::StaticKeypair> for $ttype {

        fn from(kp: $crate::macro_deps::curve25519::StaticKeypair) -> Self {

            Self(kp)

        }

    }

    /// Implementing EncodableItem, ToEncodableKey and Keygen allows this wrapper key to be stored

    /// in a keystore.

    impl $crate::ItemType for $ttype {

        fn item_type() -> $crate::KeystoreItemType {

            $crate::KeyType::X25519StaticKeypair.into()

        }

    }

    impl $crate::EncodableItem for $ttype {

        fn as_keystore_item(&self) -> $crate::Result<$crate::KeystoreItem> {

            self.$KP_NAME.as_keystore_item()

        }

    }

    impl $crate::ToEncodableKey for $ttype {

        type Key = $crate::macro_deps::curve25519::StaticKeypair;

        type KeyPair = $ttype;

        fn to_encodable_key(self) -> Self::Key {

            self.$KP_NAME

        }

        fn from_encodable_key(key: Self::Key) -> Self {

            Self(key)

        }

    }

    impl $crate::Keygen for $ttype {

        fn generate(mut rng: &mut dyn $crate::KeygenRng) -> $crate::Result<Self>

        where

            Self: Sized

        {

            let secret = $crate::macro_deps::curve25519::StaticSecret::random_from_rng(rng);

            let public: $crate::macro_deps::curve25519::PublicKey = (&secret).into();

            let kp = $crate::macro_deps::curve25519::StaticKeypair {

                secret: secret.into(),

                public: public.into(),

            };

            Ok(kp.into())

        }

    }

}

// Re-export dependencies as `tor_key_forge::macro_deps` that we use to make this macro work.

#[doc(hidden)]

pub mod deps {

    pub use derive_deftly_template_Curve25519Keypair;

    pub use derive_deftly_template_Ed25519Keypair;

    pub use derive_more;

    pub use paste::paste;

    pub use signature;

    pub use tor_llcrypto::pk::{curve25519, ed25519, ValidatableSignature};

}

#[cfg(test)]

mod test {

    use crate::Keygen;

    use tor_basic_utils::test_rng::testing_rng;

    use tor_llcrypto::{pk::ed25519::Ed25519SigningKey, rng::FakeEntropicRng};

    #[test]

    fn deftly_ed25519_keypair() {

        define_ed25519_keypair!(SomeEd25519);

        let mut rng = FakeEntropicRng(testing_rng());

        let kp = SomeEd25519Keypair::generate(&mut rng).expect("Failed to gen key");

        // Make sure the generated public key from our wrapper is the same as the

        // underlying keypair.

        let pubkey = kp.public();

        assert_eq!(pubkey.0, kp.0.verifying_key());

        // Message to sign and verify.

        let msg: [u8; 4] = [2, 3, 4, 5];

        let msg_bad: [u8; 4] = [2, 3, 4, 6];

        let sig = kp.sign(msg.as_slice());

        assert!(kp.verify(sig, msg.as_slice()));

        // Lets make sure we don't validate another message.

        assert!(!kp.verify(sig, msg_bad.as_slice()));

    }

}